void main(){
  // 变量var
  var name='Jack';
  var age=18;
  var isMale=false;
  var MaleString=isMale?'男':'女';
  print(name+age.toString()+MaleString);

  // 常量const final 区别：final：运行时常量，值在运行时赋值； const：编译期常量，值在编译时赋值
  const pi=3.14;
  print(pi);
  final double gravity=9.8;
  print(gravity);
}